If you plan to spend your vacation in Thailand, it is probably a good idea to use paper and plastic while you are there.
Since I am a regular visitor to the land of smiles, I usually have a few thousand Baht left from my previous trip. Along with that I will also bring about 500 US dollars in cash to see me through the first few days. Don’t exchange currency in your home country.
I have stopped using traveler's checks for a couple of reasons. I don’t have a local bank account; I do all of my banking online.

So, if I want to get traveler's checks, I have to pay a fee. Then I will have to pay a small fee to cash the checks at the bank. I also don’t like being restricted to accessing funds only when the banks are open.
I would never cash a traveler's check at a hotel because of the terrible rate of exchange they give. Unless you get the checks for free, I wouldn’t use them at all.

Using your credit card in Thailand is very risky. Even at the finest of hotels, the local staff is not paid much at all. It is very easy to skim and clone your credit card. It may not get used for months since the bad guys will wait until you get back home before they use it.
If you must use your credit card, keep an eagle eye on it. Don’t let it out of your site. Don’t let the hotel desk clerk take it to the back room. Don’t let the waitress take it back to the cashier. Don’t use it unless you absolutely have no other means of funds.
Using a debit card with an ATM machine is the easiest and most convenient way to acquire the local currency.

I use a separate account and transfer the funds to it a week or two before I go to Thailand. That way, I know exactly how much I have available when I arrive.
ATM machines are located about every 10 feet in Thailand and are even available in the smallest of cities throughout the country. You will get a good exchange rate and you can access them 24 hours per day.
You still need to be careful with ATM machines because bad guys are everywhere. I try to use the ATMs that are in a foyer or inside of a mall. If you access one on a small, dimly lit street at two in the morning, you are definitely risking your money and your life.
If you intend to do any online banking, do not access your account using any of the internet cafes. You never know what software is on those computers or whether someone has installed a keystroke logger to steal your password. Using your own laptop will be as secure as it is at home.

It is best to complete as much of your online financial transactions before you go, just to be safe.
So, you should use a combination of paper and plastic on your Thailand vacation. Bring some of your home currency to cover you during your first couple of days. You can exchange this at the Thai airport at any of the currency exchange booths. If you don’t want to carry that much cash, you can always use your debit card at the airport ATM machines.
For your day to day funds, I would again use the ATM machines. Do this during the day for additional security and make sure that you keep your plastic locked up in the safe along with your passport, plane ticket and any other valuables.
Remember to only carry as much cash as you will need for your day or night activity and the rest in the safe. You can always go back to your room if you need additional funds.
If you have any Baht left over at the end of your trip, you can exchange it at the Suvarnabhumi International Airport in Bangkok, or keep it stashed away for your next Thailand holiday.